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Securing your XDC Masternode (Running on Ubuntu 20.04LTS)

Note: Although this guide refers to masternodes, it will also work for standby nodes as well as non-validator nodes (as long as they are reachable via a public IP address). For non-validator nodes using HTTP/Websocket JSON-RPC connection, you'll also need to take into account your specific port access requirements when dealing with ports 8888 and/or 8989.


XDC network masternodes are important because they validate transactions, help to maintain the network's security and integrity, and ensure that the network runs smoothly. Securing your node will help with all of these issues.

From a high-level consideration, to secure your XDC masternode you would need to:

  1. Keep it up-to-date with the latest security patches.
  2. Use a strong and unique password.
  3. Change your SSH port and enable firewall rules to restrict access to the node.
  4. Use SSL/TLS encryption to secure communication with it.
  5. Implement access controls to limit who can interact with it.
  6. Regularly monitor it for any suspicious activity or unauthorized access attempts.

We will deal with each of these in turn below.


Keeping your node up-to-date with the latest security patches

This has 2 components. Component 1 is the server OS. Component 2 is the XDC client.

Regarding the Server OS

As per XinFin's original XDC network node setup instructions deploying an XDC node by the Docker method is supported on CentOS, RedHat Enterprise Linux (latest release) and Ubuntu 15.04+.

Each OS vendor has a period for which its product is supported. For example we can see in the image below that Ubuntu 20.04LTS has hardware and maintenance updates until 2025 as well as Extended Security Maintenance until 2032. Ensure your OS is supported with current updates.

Ubuntu LTS Release Cycle

To update the OS packages on your server we first need to connect to the remote server so we can then do all the following steps on the remote server. Remember to replace “root” in this command with your actual username for the remote server, and replace ip.address with the actual IP address of the remote server:

ssh -lroot -p22 ip.address
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Update the OS packages:

sudo apt update -y && sudo apt upgrade -y && sudo apt autoremove -y
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Many OS updates often require you to reboot your server, but we must first stop the XDC client. To do this, first change to the Mainnet client directory:

cd ~/XinFin-Node/mainnet
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Stop the XDC client:

sudo ./docker-down.sh
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Reboot the server:

sudo reboot
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You’ll notice this has disconnected your Terminal from the VPS while it reboots. Allow enough time for the VPS to reboot, then reconnect to your VPS as you normally would. Remember to replace “root” with your actual username for the remote server, and replace ip.address with the actual IP address of the remote server:

ssh -lroot -p22 ip.address
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Change to the Mainnet client directory:

cd ~/XinFin-Node/mainnet
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Start the XDC Client:

sudo ./docker-up.sh
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Logout of your server:

logout
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Regarding the XDC Network Client

Connect to your VPS as you normally would. Remember to replace “root” with your actual username for the remote server, and replace ip.address with the actual IP address of the remote server:

ssh -lroot -p22 ip.address
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Change to the Mainnet client directory:

cd ~/XinFin-Node/mainnet
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In the Mainnet client directory there is a script we can run to upgrade the XDC network configuration scripts and the Docker images. Note that as part of the process it will stop and start the XDC client, so expect to see your peers drop on the XDC Foundation Network Stats page. To run the upgrade script:

sudo ./upgrade.sh
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Logout of your server:

logout
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Using a strong and unique password

The time it takes to guess passwords by brute force depends on the length and complexity of the password, as well as the computing power of the attacker. It can range from a few seconds to several years or even centuries (or even longer!).

As per the image below (sourced from Hive Systems), in 2023 an 18 character password consisting of only numbers can take as little as 6 days to obtain by brute force. Using the same length password but including random numbers, upper and lowercase letters as well as symbols, can increase the brute force time to 26 trillion years with the same computing power.

Hive Systems Password Brute Force Times

Ensuring that a password is not reused is also important. If the same password is used on multiple sites then if ANY of those sites are compromised and your password is somehow obtained, it could potentially allow unauthorised parties to access other accounts/services where you have reused the same password.

If you have difficulty generating a random password with the criteria described above, there are online password generators from reputable vendors. One example of this is the Norton Password Generator

Norton Password Generator

If you already have an existing password and would like to change it, you can do so by first connecting to your VPS as you normally would. Remember to replace “root” with your actual username for the remote server, and replace ip.address with the actual IP address of the remote server:

ssh -lroot -p22 ip.address
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Change your password with the following command. Replace <username> with the actual username of the user whose password you want to change. You will be prompted to enter and confirm the new password:

sudo passwd <username>
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Logout of your server:

logout
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Note: another alternative is to setup ssh key-based authentication and then to disable the ability to use password logins. This will not be covered in this article. If there is demand, I'll consider covering it in a future article.


Change your SSH port and enable firewall rules to restrict access to the node

Securing the server ports and RPC endpoint is important to prevent unauthorized access and potential security breaches such as execution of malicious code.

XDC Network Andromeda Upgrade

Those who were around at the time may remember that the Andromeda update to the XDC network implemented an upgrade to Geth 1.9.X.
From examining an XDC node's docker-compose.yml file shown in the image below, we can see that Geth nodes on the XDC network use:

  • Port 30303 for RLPx(TCP)/UDP peer-to-peer communications allowing node discovery and connection to peers
  • Port 8989 for HTTP JSON-RPC API which allows external applications to interact with the XDC blockchain
  • Port 8888 for secure Websocket communications to the XDC blockchain

XDC Node docker-compose.yml

In addition Linux servers normally have their SSH port set at 22 by default, and this is used to connect to the server and access its command line.

For the purposes of this article, we will assume that your masternode is being used only for the purpose of maintaining the XDC blockchain and does not require RPC/Websocket access for external applications to use.

Based on the above, the best way of securing our node with a firewall is to:

  • Change our SSH port from 22 to a different number to make it harder for random malcontents to connect
  • Use a firewall to block ALL incoming ports
  • Then open ONLY ports 30303 and our new SSH port
  • We will leave ports 8888 and 8989 blocked (filtered) as we are assuming that these are not needed as noted above

To change the port used for SSH on Ubuntu, you need to first connect to your VPS as you normally would. Remember to replace “root” with your actual username for the remote server, and replace ip.address with the actual IP address of the remote server:

ssh -lroot -p22 ip.address
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Next you need to edit the SSH configuration file located at /etc/ssh/sshd_config :

sudo nano /etc/ssh/sshd_config
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Look for the line that says "Port 22". If there is a # before "Port 22" as in the image below, you'll need to delete the # symbol:

Image description

Change the number 22 to whatever new port number you want to use for SSH connections:

Image description

Save the file:

Press "CTRL+X"
Press "y"
Press "ENTER"

Then restart the SSH service:

sudo service ssh restart
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Note: Whenever we have previously used "-p22" as part of our command to connect to a VPS via SSH, this is specifying to ssh what port the remote server is using for ssh. From now on whenever you connect to your XDC node, you will need to change the 22 in "-p22" to your new port number instead.

UFW Uncomplicated Firewall

Now to implement a firewall we will use UFW (Uncomplicated Firewall) which is a front-end tool for managing firewall rules on Ubuntu.

First we need to install ufw:

sudo apt install ufw
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Next we establish our default policies to block ALL incoming traffic and only allow outgoing traffic:

sudo ufw default deny incoming
sudo ufw default allow outgoing
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Then we open up port 30303 so the XDC client is discoverable by peers:

sudo ufw allow 30303
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IMPORTANT: Next we need to ensure that we open up our SSH port (22 or whatever port number you changed it to):

sudo ufw allow <yourSSHport>
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Lastly we need to enable UFW:

sudo ufw enable
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Reboot your server:

reboot
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Now ssh to your server to test your new port number instead of 22 and ensure that you can connect ok.

If you are unable to connect and need to get back to the command line on your server to modify the firewall details, most VPS providers will have a console for the server directly accessible through their VPS control panel. So you just need to go to your VPS provider website, login and find the console for the VPS running your XDC client. Then login and do what you need to do.

After rebooting, we will need to restart the XDC Mainnet client, so first we need to SSH to our VPS:

ssh -lroot -p<yourSSHport> ip.address
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Change to the XDC Mainnet client directory:

cd ~/XinFin-Node/mainnet
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Restart the XDC Mainnet client:

sudo ./docker-up.sh
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Then logout of your VPS:

logout
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Note: In another planned future article we will be making some further adjustments allowing certain IP addresses restricted access to port 8989 (HTTP JSON-RPC) in the firewall rules.


Use SSL/TLS encryption to secure communication with the node

SSL/TLS encryption makes things safer if external applications are using the JSON-RPC (HTTP/Websocket) functionalities of your node to communicate with the XDC blockchain. The assumption of this article is that your node is not being used for this so this issue will not be discussed here. If there is demand I will explore it in a future article


Implement access controls to limit who can interact with the node

This involves configuring firewall rules to restrict access to the node from specific IP addresses or networks and we will be playing with this shortly in an upcoming article where we will be allowing restricted access to specific ports from only certain whitelisted IP addresses.


Regularly monitor it for any suspicious activity or unauthorized access attempts

You can regularly monitor an XDC node for any suspicious activity or unauthorized access attempts by setting up alerts and notifications for any unusual activity and regularly reviewing logs and metrics. Additionally, you can consider using third-party security tools and services to enhance your node's security. Usage of monitoring should not however replace implementing security best practices such as using strong passwords and keeping your software up to date.

Many VPS providers will have some kind of VPS monitoring in place which is already accessible via their control panel and generally includes alerts when certain preset VPS parameter limits (eg CPU usage, memory usage, network traffic, disk I/O) are breached. If your VPS provider does not provide this, third party solutions such as Netdata can be used to provide it. Use of Netdata will not be covered here. If there is demand I will cover it in a future article.

Fail2Ban

Implementing the fail2ban linux package can also be useful for keeping your node safe by blocking IP addresses that attempt to access the node with incorrect login credentials or perform suspicious activities.

Install fail2ban:

sudo apt install fail2ban
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Next we create a copy of the configuration file for us to customise:

sudo cp -p /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
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Open the new file in nano so we can configure fail2ban:

sudo nano /etc/fail2ban/jail.local
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Scroll down until you find this sshd section:

The SSHD section you are looking for

Replace the 3 white lines shown above with all of these lines:

enabled = true
filter = sshd
port = ssh
banaction = iptables-multiport
findtime = 86400 # 86400 seconds = 1 day
bantime = -1 # -1 = ban forever
maxretry = 3 # 3 attempts in 1 day = ban
logpath = %(sshd_log)s
backend = %(sshd_backend)s

Reconfigured fail2ban

Save the file:

Press "CTRL+X"
Press "y"
Press "ENTER"

Restart fail2ban:

sudo systemctl restart fail2ban
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Logout of your server

logout
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Commands to use fail2ban

To check who is banned:

sudo fail2ban-client status sshd
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To unban an IP address:

sudo fail2ban-client set sshd unban <ip address>
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If you manage to ban yourself by using incorrect passwords etc, you can use the direct console on your VPS provider's control panel to access the command line of your VPS (same as described in the Firewall section above) and unban your IP address using the above command.

(Special thanks to go140point6 GitHub re fail2ban)


In conclusion, securing XDC nodes is crucial to protect the network from potential attacks and ensure the safety of user funds. By implementing the methods discussed in this article, such as using strong passwords, enabling firewalls, regularly updating software, and using monitoring tools, node operators can significantly increase the security of their nodes. It is important to stay vigilant and proactive in maintaining node security to prevent any potential breaches. With these measures in place, the XDC network can continue to operate securely and efficiently.

In case of any technical queries on XDC Network, feel free to drop your queries on XDC.Dev forum.

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